1. (Field of the Invention)
The present invention relates to a starting apparatus, a starting method, and a control method of an internal combustion engine. They comprises a main air passage (intake air passage) for the engine, a bypass air passage provided in parallel to the main air passage, a means for supplying vaporized fuel to the bypass air passage at the time of start-up cranking, and also to an exhaust filtration apparatus of an internal combustion engine equipped with the starting apparatus.
2. (Prior Art)
Generally, at the time of state where an internal combustion engine has not been warmed up yet (This state is called as “cold state of the engine” fuel injected from the injection valve mostly adheres onto the intake passage wall and cylinder wall of the engine. Accordingly air-fuel mixture around the ignition plug in the cylinder becomes leaner, thereby ignitability and combustibility of the fuel deteriorate. If the fuel supply is increased so as to prevent the leanizing of air-fuel mixture around the ignition plug, more fuel adheres onto the cylinder wall. Accordingly after the warming up of the engine, excessive fuel is supplied to the engine, and a lot of unburnt vaporized (HC) is exhausted.
Prior arts for preventing this problem are disclosed in the Japanese Application Patent Laid-open Publication No. Sho 63-150465 (1988) and Hei 7-139455 (1995). These prior arts have an auxiliary injection valve and an electric heater installed in a bypass passage that bypasses the throttle valve in the intake air passage. The heater is energized at the time of a cold state of the engine to facilitate vaporization of the fuel. Hence no fuel adhesion is caused, and it prevents the combustion of the engine at start-up from deteriorating, and HC emission is reduced. In these prior arts, at the starting time of the engine, a throttle valve installed in the main air passage closes, and the bypass air control valve installed in the bypass passage (here, the cross area of the bypass passage is smaller than that of the main intake air passage) opens. Thereby the high-velocity airflow is generated in the bypass passage, and so atomization of the flowing fuel and vaporization of the fuel adhered onto the heater surface can be facilitated. Further, no heater is installed in the main air passage. Accordingly the resistance of the airflow passage at high velocity becomes lower, and the fall of engine power can be also prevented.
In an ordinary multi-point injection (MPI) system, liquid fuel is injected atomizing by a fuel injection valve installed near the intake port of each engine cylinder. The injected fuel mostly adheres onto the intake passage wall, the intake valve and the cylinder wall. The fuel adhesion onto these walls causes to decrease the fuel amount to be supplied in a gaseous phase around the ignition plug. Hence, the ignitability and combustibility are deteriorated. On the contrary, with a system where fuel is heated and vaporized by a heater and then supplied to the cylinder, it is generally known that, because no fuel adheres onto walls, the ignitability and combustibility improve remarkably, particularly at the time of the cold state of engine, and so unburnt vaporized (HC) emission reduces.
An example starting apparatus of a conventional internal combustion engine is explained hereunder, using FIG. 9. The intake passage of the internal combustion engine comprising:
a main air passage 3, that consists of a intake passage 1, a surge tank 2, and a manifold passage 3a branched downstream of the surge tank 2 and connected to the intake ports 10 of respective cylinder (FIG. 9 shows one pipe among the manifold 3a),
a bypass air passage 4 installed in parallel to the main air passage 3 and connected close to the intake port of each cylinder,
fuel injection valves 5 installed near the intake ports of respective cylinders or installed directly in the respective cylinders,
an auxiliary fuel injection valve 6 installed in the bypass air passage 4, and a bypass air control valve 7 capable of adjusting the incoming air quantity into the bypass air passage. A throttle valve 8 is installed in the intake passage 1 and an air cleaner 9 is installed upstream of the throttle valve 8. Besides, a heater 15 is provided to heat and vaporize the fuel injected from the auxiliary injection valve 6.